title: Antimicrobial efficacy of multi-purpose contact lens disinfectant solutions following evaporation.
abstract: OBJECTIVE
  Non-compliance is a significant factor in contact lens related microbial keratitis and includes solution reuse and failure to recap the lens storage case resulting in evaporation effects. To address this, impact of partial evaporation on the antimicrobial efficacy of multipurpose contact lens care solutions was investigated.
  
  
  METHODS
  Solutions were evaporated under a stream of air to 2× and 4× concentration and challenged with Fusarium solani (ATCC 36031), Candida albicans (ATCC 10231) and Acanthamoeba castellanii (ATCC 50370). The level of organism kill at 6h was compared to the non-evaporated product.
  
  
  RESULTS
  ReNu with MoistureLoc(®) (RML) lost 90-100% of biocidal activity against C. albicans on evaporation, 75-99% for F. solani and 29-33% with A. castellanii at 2× or 4× concentration, respectively. OPTI-FREE(®) RepleniSH(®) lost 72-90% efficacy against C. albicans and F. solani, and 61% at 2× and 10% at 4× concentration with A. castellanii. ReNu(®) MultiPlus, AQuify(®) Multi-Purpose and Biotrue™ showed only loss in efficacy with C. albicans at 4× concentration giving 79%, 34.5% and 48% reduction, respectively. No loss in biocidal activity on evaporation was obtained with Complete(®) Revitalens for all organisms.
  
  
  CONCLUSIONS
  Partial evaporation can affect biocidal efficacy of multi-purpose solutions and may have been a significant factor in an outbreak of Fusarium keratitis cases associated with RML. Evaporation results in increased binding of cationic disinfectants to counter-ions in the formulation, reducing ability to attach and rupture anionic microbial cell walls. Interaction may also occur between the biocidal ingredient and other components, such as surfactants, resulting in sequestration of activity through micelle formation.
authors.affiliation: Abbott Medical Optics Inc., Santa Ana, CA 92705-4933, USA. sk46@le.ac.uk
authors.forename: Simon
authors.initials: S
authors.lastname: Kilvington
authors.forename: Charles H
authors.initials: CH
authors.lastname: Powell
authors.forename: Anthony
authors.initials: A
authors.lastname: Lam
authors.forename: James
authors.initials: J
authors.lastname: Lonnen
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D018407:Bacterial Physiological Phenomena / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D018639:Contact Lens Solutions / Q000737:chemistry* / Q000494:pharmacology*; D003890:Desiccation
chemical_list: D000900:Anti-Bacterial Agents; D018639:Contact Lens Solutions